| A | B |
|---|
| Big Bang Theory | The sudden event which took place 10 billion to 20 billion years ago causing the universe to begin expanding. |
| Inner Core | Layer of the earth which is extremely hot and solid. It consists mostly of the heavy metals iron and nickel. |
| Moho | The boundary between the solid crust and the liquid mantle. |
| Collision Hypothesis | Explanation of how the earth formed when a star passed too closely to the sun |
| Mantle | The outer core and this layer of the earth consist of hot |
| Dust Cloud Hypothesis | This explanation of the formation of the earth says that the solar system formed from a huge cloud of gas and dust in space. |
| Crust | Layer of the earth which makes up 1% of the earth’s volume. It is the layer upon which we live. |
| Outer Core | Liquid layer of the earth which is made of iron and nickel and is extremely hot. |
| asthenosphere | upper portion of the mantle where the molten rock flows in convection cells. |
| convection | The heating,rising,spreading,cooling and sinking of molten material within the asthenosphere |
| lithosphere | Another name for the earth’s crust. |
| hydrosphere | The “sphere” which is made up of all of the water on earth. |
| Oxygen | The most abundant element found in the earth’s crust. |
| 23.5o | The earth is tilted on its axis at this angle. |
| equator | 0o latitude. |
| latitude and longitude | The two coordinate used to find a location on the surface of the earth |
| Polaris | Scientific name for the North Star. |
| Ursa Major | Big Dipper |
| Ursa Minor | Little Dipper |
| altitude & azimuth | the height and direction of an object in the sky |
| Zenith | Position located at 90o altitude or directly overhead. |
| latitude | Lines that run north and south of the Equator. |
| quadrant | Instrument we use to measure the altitude of an object in the sky |
| well | Object in the city of Syene which Eratosthenes used to figure out the circumference of the earth. |
| Prime Meridian | 0o longitude |
| longitude | Lines that measure east and west of the Prime Meridian. |
| 15 o | A time zone includes this many degrees of longitude. |
| 24 | Number of time zones on earth. |
| 4 | The number of time zones within the continental United States |
| 3 | Number of hours difference between Cleveland and Los Angeles |
| rotation | Day and night are caused by earth’s ___________________. |
| 1000 | The earth spins on its axis at this speed (mph). |
| 365.25 | Length of time it takes earth to make one complete revolution around the sun. |
| sun stops | The term “solstice” means ________ ___________. |
| equal nights | The term “equinox” means ____________ ______________. |
| summer solstice | The point in the earth’s revolution around the sun when the northern hemisphere is tilted toward the sun and receives the most direct rays of the sun. |
| vernal equinox | March 21st when the earth is neither tilted toward nor away from the sun and both the Northern and Southern Hemispheres receive equal amounts of the suns rays. |
| autumnal equinox | September 21st when the earth is tilted neither toward nor away from the sun. |
| winter solstice | Point in the revolution around the sun when the northern hemisphere is tiled away from the sun. |
| ellipse | The shape of the earth’s orbit around the sun. |
| aphelion | July 4th, when the earth is farthest away from the sun (approximately 94 |
| perihelion | January 3rd, when the earth is closest to the sun. |
| month | The moon’s orbit around the earth gives us this unit of time. |
| universal gravitation | The pull or force of attraction between universal bodies. |
| gravity | The force of attraction between earth and objects on it. |
| oblate spheroid | Shape of the earth; a somewhat distorted sphere. |
| inclination | The tilt of the earth on its axis. |
| circle of illumination | The imaginary line on the surface of the earth that separates day and night. |
| orbit | The elliptical path that earth follows around the sun. |
| precession | The slow wobble of the earth on its axis. |
